Depending on what thickness you want, either cheap plastic notebook/folders from Walmart or peak antifreeze jug plastic will work.
I thought PR4 fans might find this comparo interesting. Top to bottom: Bark River Kephart, Lon Humphrey Kephart, PR4:
Yup. Well aware of that - I've been a fan of Kephart styles for a long time. But I think it's worth seeing the PR4 alongside more traditional Kephart interpretations.
Id imagine an uncoated blade has less resistance than a coated blade. So if thats the case id say an uncoated will cut better.
Corrosion resistance seems to be better though. Ive neglected the cleaver and PR4 and not had any signs of it. On the screws of the cleaver once though.